Dangers of Long-term Marijuana Use

A newly released study indicates the dangers of long-term marijuana use. The bottom line is that it alters brain cells.

The study was published in Jneurosci (The Journal of Neuroscience) on October 16. The researchers focused on the ventral tegmental area (VTA) of the brain. Dopamine and serotonin receptors are concentrated there. Those receptors give a person the sensation of pleasure.

The scientists conducted the study on mice in their “teen” and “adolescent” stages of life. The mice received injections of THC (Tetrahydrocannabinol) every day for a week. THC is the principal psychoactive ingredient in marijuana. Marijuana (as well as opioids and alcohol) stimulates the VTA to release dopamine resulting in an experience of pleasure and the desire for more. There is a GABA (gamma-aminobutyric acid) cell in the VTA which acts as an inhibitor. When the brain releases GABA, it serves to restrain the desire for pleasure and keep it under control.

In the week of receiving THC, the GABA neurons lost their ability to control the desire for pleasure. They were in a state of “long-term depression” (LTD). This caused the dopamine to remain longer in the VTA giving a sense of being “spaced out,” and leading to addiction.

The researchers stated that the long-term effect of the THC was to remodel the brain’s synapses resulting in reduced “synaptic plasticity.” The synapses carry electrical or chemical signals from one nerve cell (neuron) to another. This “synaptic modification” is changing the brain at the cellular level.

The Diagnostic and Statistical Manual of Mental Disorders (DSM) is published by the American Psychiatric Association, and it is the standard reference used by mental health professionals at all levels. The current edition is DSM-5. It defines cannabis (marijuana) use disorder as a “problematic pattern of cannabis use leading to clinically significant impairment or distress.”